Potassium-fluorine glasses



l. MOCKRIN I'AL POTASSIUM-FLUORINE GLASSES June 24, 41958 5 Sheets-Sheet 1 Filed Feb. 27. 1952 IN V EN TOR.

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4 POTASSIUM-FLUORINE GLASSES Filed Feb. 27, 1952 5 Sheets-Sheet 4 RELATION OF AIgOa, SIOa, AND B20; CONTENT TO FLUORINE IN GLASS COMPOSITION CONTAINING FLUORINE, K10, SIOZ AND AT LEAST ONE OF THE OXIDES Algo; AND B203 IN WHICH THE FLUORINE IS PRESENT IN AMOUNTS OF I4 TO 32 WEIGHT PERCENT, THE KzO IS PRESENT IN AMOUNTS OF I2 TO 26 WEIGHT PERCENT, AND THE FLUORINE TO KgO RATIO IS IN THE RANGE OF I.O TO L4.y

IAWRE IOOKIIN WILLIAN l. KNAPP June 24, 1958 Filed Feb. 27. 1952 I. MOCKRIN ETAL 5 Sheets-Sheet 5 RELATION OF AIgOg, SiO; AND BgOg CONTENT TO FLUORINE IN PREFERRED GLASS COMPOSITIONS CONTAINING FLUORINE, K10, S101, AIIC. AND B10; IN WHICH THE FLUORINE IS PRESENT IN AMOUNTS OF 2| TO 2B WEIGHT PERCENT, THE K10 IS PRESENT IN AMOUNTS OF I7 TO 25 WEIGHT PERCENT, AND THE FLUORINE TO KgO RATIO IS WITHIN THE RANGE OF LO TO L4.

ISADORE IOCKRIN WILLIAU S. KNAPP 2,840,481 ilorAssiUM-FLUoniNn GLASSES Isador Mockrin, Philadelphia, Pa., and William J. Knapp, Los Angeles, Calif., assignors to Eennsalt Chemicals Corporation, a corporation of Pennsylvania Application February 27, 1952, semi No. 273,671

7 claims. (ci. ien- 42) This invention relates to novel potassium-'llurine glasses and methods of making the same and to improved enamel compositions suitable for forming protective and decorative coatings on aluminum and aluminum base metals.

Aluminum and aluminum base metals are being employed in ever increasing variety for a great many purposes. Moreover, the volume of production of these materials has been so increased that their price has been reduced suiiiciently so that they now oier considerable competition to steel and other iron materials generally used in building construction for the manufacture of panels, decorative trims, etc., or for the making of various articles `of manufacture where lightness combined with strengthand durability is desired.

However, aluminum is a relatively soft metal, particularly as compared with iron or steel. As a result, any unprotected aluminum surface is easily marred by scratching or impact with other objects. Also, there is tendency for the aluminum surface to become pitted when exposed to the atmosphere for extended periods of time. rl`his is particularly true if the surface is subjected to periodic cleaning. Further, the softness of the aluminum permits Vthe relatively easy vremoval of the natural protective oxide layer which forms on the aluminum surface with the result that the relatively chemically active aluminum is exposed and the surface thus further marred.

States atene() t This is particularly undesirable when the metals are used for panelling or decorative purposes in places where they are subject to periodic cleaning with materials which contain mild abrasives.

In order to overcome these objectionable features of aluminum and aluminum base alloys attempts have been made to form protective enamel coatings thereon similar to those used on iron and steel. Besides protecting the aluminum or aluminum base metal, an enameled surface has an added advantage from the decorative point of view in that it can be attractively colored through the addition of coloring agents.

Vitreous enamels of the type commonly used with other metals, particularly with iron or steel, are unsatisfactory for the enameling of aluminum surfaces since their fusion temperatures are too high to enable them to be used satisfactorily with a metal having as low a melting point as aluminum. 0f the various vitreous enamel compositions which have heretofore been tried for enameling aluminum and aluminum base metals, we are aware of only one class of enamels which is reputed to have a sufficiently low fusion temperature, sufficient adherence to aluminum and aluminum base metals and suicient resistance to chemical action to be used for forming protective coatings on these metals. However, this class of enamels contains as one of its principal ingredients over 25% lead oxide, which has long beeny known to possess toxic properties. In some of the formulations the lead oxide content is as high as 60% by weight. In addition to its being objectionable because of its toxic properties, lead oxide is relatively expensive and due to s 2,840,48i Ice liatented June 24, 1958 Vcomponent systems 'are exceedingly diicult to illustrate. YIn order to illustrate the invention more easilyha four component system is used, SiO2-A1202f-B2'03l-K2'SiF. This can be represented by a tetrahedron in which, for convenience, K2SiF6 is placed at an apex. By representing the system in this manner the eiect of varying the A1203, B203 and Si02 can be further illustrated by xing the Vamount of K2SiF6 and illustrating the system by a triangle in which only the amounts of A1203, B203 and Si02 are varied. For an exact presentation, a new triangle would have to be used for each change in K2SiF6 content. This method of description has the disadvantage of fixing the ratio of the iluorine to potassium and only partially showing the elect of varying the amounts of these materials. However, it does illustrate the large number of glasses which can he formed as well as the general effect of varying the amounts of added Si02, A1203 and B202 and the limits of these materials. The figures in the drawings are based on this system of illustration.

Figure la is a, tetrahedron representing the four component system K2SF6, Si02, B202 and A1202 with the and planes indicated. v v Fig. l is aV graph representing the 30% K2SiF8, 50% K2SiFG, and 70% K2SiF6 planes of Fig. -la showing 'the glass forming characteristics of various compositions indicated by the points on the graph.

Figure 2.a is a tetrahedron representing the 'four component system K2SiF2, Si02, A1203, B202, the 50% K2SiF6 plane being indicated. V

Figure 2 is a graph representing the 50% K2SiF2 plane of Figure 2a showing the fusion temperatures of the various compositions indicated by the points on the graph. The purpose of Figure 2 is primarily to illustrate the elects of the ingredients A1203, Si02 and B202 on-fusion temperature.

Figure 3 is a graph illustrating4 the eiect of the ratio of Si02 added as such to the calculated B203 on the fusion temperature and durability of glasses. This is done by selecting glasses of two different A1202 contents onthe 50% K2SiF6 plane of Figure l and varying the Si02 and B203 content of these glasses.

Figures 4a, 4b, and 4c are graphs pictorially 'representing the broad limits respectively of A1203, Si02, and B203 as related to uorine content in the glasses `of the present invention. 1

Figures 5a, 5b, and 5c are graphs pictorially representing the preferred limits respectively of A1203, Si02, and B203 as related to iluorine content in the glasses of the present invention.

Referring to the drawings Figures l and 2, a ceramic chemist will readily note that the points noted in the graphs give actual compositions.

Referring to Figure l each point noted gives three compositions, one for 70% K2SiF6, one for 50% K2SiF6, and one for 30% K2SiF6, the 70, 50 and 30 of the point representing the 70% K2SiF6 plane, the 50% K-2SiF6 plane, and the 30% K2SF6 plane as illustrated by the in the middle ofthe graph of Fig. `l, this represents the following three different compositions:

10% msm, 50% msm. 30% Kisirs plane plane plane Percent Percent Obrvation devitrltled glass stntered These composition are read directly from the graph of Figure `1. A1303, SiO-3, and B303 must add up to 100% in order to get the correct amounts `of Vthese oxides, in the compositionwhere 70% of the composition is K3SiF3 the remainder vof the composition is obtained by multiplying the values read for A1303, ,Si03, and B303 by 30%. When'K3SiF3 is `50% these values will bev multipliedby 50% and Where the K3SiF3 content is 30% these values will be multiplied by 70% toget the amounts of.Al303, Si03 and B303 in the composition. The graph of Figure 1 thus gives actual compositions and indicates whether these compositions formed a glass (G), a devitritied material (D)`,`,or a sintered material (S).

Referring to Figure 2 illustrating the 50% K3SiF3 plane, the points indicated are actual glass compositions, determined as in the same manner as for the 50% K3SiF3 plane of `Figure 1, for which the fusion temperatures are given. t

The glasses, which form the subject matter of our present invention, are prepared from batches which will yield,` on a calculated weight basis of 100 parts glass composition, a glass containing about 14 to 32 parts of iluorine` and 12 .to 26 parts of K30 in a weight ratio of 1.0 to 1.4 parts uorine per part K30, together with approximately 7 to 66 parts Si03, 0 to 33 parts A1303 and to 66 parts B303. All values are given on a weight basis,` it being understood that wherever parts, percents or ratio are referred to throughout the specification and claims these are on aweight basis and not on a mol or volume basis.

It is immediately apparent on studing the projection of the tetrahedron of Figure l that the limits with respect to the amounts .of A1303, `13303 and Si03 present in the glass composition are dependent on the amount of potassium and fluorine also present, a considerably larger variation with respect to the A1303, B303 and Si03 being permissible when the total calculated fluorine content of the glassis approximately 231%,` which it is for 50% K3SiF3,lthan when it is either 14% or 32%, which are the lluorine contents respectively when 30% K3SiF3 and 70% K3SiF3 are employed. The limits both in the specifcationand claims should, therefore, be read with this in mind.

This relationship between the amounts of A1303, Si03, and B303 to the uorine contentof the glass is illustrated in a `somewhat different manner by Figures 4a, 4b, 4c and Figures 5a, 5b and 5c,` the figures of set 4 indicating the broad limits of the glasses claimed and the figures of 5 indicating the preferred limitsof the glasses claimed. It will be noted, that even though the glasses may contain no A1303 or no B303 in the broad limits of 4the composition, they must contain one or the other and preferably both.

Since by nature of the graph, the percents of It will also be noted that the fluorine to potassium ratio is indicated in the legend on the drawings.

These figures thus help to illustrate the boundaries of the glasses of the present invention rather than giving specific compositions as do Figures l and 2;

Though the glasses and enamels of our present invention all contain, on a calculated basis, fluorine, K30, Si03, A1303 and B303 in amounts in the ranges above specified, this does not mean that the glasses are limited to these ingredients alone. VThis is clearly illustrated by glasses of the following Vtable which lists some of our glass compositions together with their fusion temperatures. The calculated glass compositions are given on a weight basis. The fusion temperatures were obtained by the fusion block method (A. L. Andrews, Enamels, p. 331, The Twin City Printing Co., Champaign, Illinois, 1935).

lA 513203 Fusion Temp., 0.

Our preferred glasses are those having relatively low fusion temperatures and from which we would generally prepare our enamel frits. These preferred glasses generally contain on a calculated oxide basis 17 to 23% K30, l1 to 38% Si03, 5 to 33% A1303, 2 to 43% B303 and 21 to 28% iluorine, the weight ratio of uorine to potassium oxide being within the range of about 1.0 to 1.4.. In calculating these percentages from the batch ingredients employed, we prefer to use the following method.

Assuming a batch composition, silica (Si03) 6.0%, alumina hydrate (A1303.3H30) 19.0%, boric acid (H3B03) 32.1% and potassium uosilicate (K3SiF3) 42.9%, the calculation is made by using the oxide equivalents of the potassium uosilicate (K3SF3). By this method of calculation, the glass would be described as one having a calculated oxide content of Si03 19.9%, A1303 14.0%, B303 20.4%, K30 20.7% and F 25.1%. This is. the method of calculation used for the herein described limits and for the glass compositions given in the above table. The method is that usually used in describing glasses.

It should be pointed out, however, that other methods of calculation could be used and somewhat different results obtained. It is, therefore, important, in considering the limits as set forth in the specification and claims, that it be understood that these limits are based on the oxide method of calculation as illustrated.

If the calculations are made by frstrassuming that the K3SiF3, of the above batch, is present in the final glass as KF and SiF3, the iinal calculated Si03 content and calculated fluoride content of the glass would be somewhat different `than that obtained by using as a basis for calculation, oxide equivalent of the K3SiF3. This is readily .illustrated by the following example: Using the same batch ingredients but ,assuming the K3SiF3 to be present in the final glass as KF and SiF3, the glass on a calculated basis would contain S103 7.6%, A1303 15.6%, B303 22.8%, SiF4t 25.5% and KF 28.5%. The glass, by this method of calculation, would have a fluorine content of 28.0% and a Si03 content of 7.6% as compared to the fluorine content of 25.1% and the Si03 content of 19.9% as obtained by the first described method of calculation.

asacaai ably greater chemical resistance, particularly toalkalis, `than the unprotected aluminum oraluminum base metal to which they are applied.

In making the glasses used for preparing the diagrams in the drawings and used for illustration in the :tables and examples of the present invention, the l tp'iovvdered `batch ingredients were weighed out, thoroughly. mixed and then `placed in clay or kyanite crucibles. vThe crucibles were then placed in a furnace in'which the temperature was about 1000 C. Though generally a clear liquid was formed inabout minutes, vthe. crucibles were usually left in the furnace for about one hour. After this time they were removed and permitted to cool gradually if a .glass wasrdesired, or the molten .contents of the rCrucible were cooled rapidly by pouring into water if a frit was desired. The clay or kyanite crucibles showedl substantially no signs lof damage after Iring-y which is surprising in View of the high tluorinecontent of the, glassesprepared. This is probably .due to the formation of a protective coating during the Ipreparation of the melt which protects theI inner surfaceqof the Crucible from the main body of the melt.

One interesting aspect noted with respecttothe system of glasses .of our present invention is that the ratiopf the Si02, added asSiOg to the batchingredients, ftothe B203, on-a calculated basis, has an'important .effect on the fusion temperature of the final glass .as well as on its resistance to chemical attack.

For example, as this ratioincreases, the fusion temy'perature of the glass tends to increase and .as'theratio decreases the fusion temperature of the ',glassftends l'to decrease. However, since the durability of the glasses tends to decrease as the Si02/B203 ratio decreases, it is preferred to worlr with glasses having a 4Si02/B2O3 ratio of at least 1 (the SiO-z being that added as such Vand not the total calculated SiOZ of the glass). The effect of lvariation of this ratio on. the fusion temperature and durability of glasses of the system A1203- B203-'SiO2-K2SiF6, where the A1203 is held to 17.5% and 22.5%, respectively, and the KZSiFG is held to is illustrated in Figure 3 of the drawings.

Though in Figure 1, the fluorine and potassium content of the glasses are represented as being obtained through the use of KZSiFS, the fluorine and potassium arenot limited to this fured weight vratio of 1.5,

but may vary from 1.2 to 1.7 parts uorine per part potassium (equivalent to a weight ratio of 1.0 to 1.4 parts fluorine per part potassium oxide). Also, the potassium and fluorine may be added to the glass by substituting in place of the KZSiFs, either in whole or in part, various raw materials such as KBF4, KF, K2AIF5, etc., as long' as the potassium and fluorine-containing additions are added in such amounts as to keep the desired iluorine to potassium ratio and the calculated oxides in the ranges disclosed.

`In making the glasses of our present invention, we generally prefer Vto use in the batch ingredients K2SiF6 for introducing the iluorine and K20; K2SiF6 and SiOz for introducing the Si02; A12O3-3H20 and A1203 for introducing the A1203; and HSBOS for introducing the B203. However, in the formation of glasses, once the glass composition has been determined, it is common to use various materials in the batch to introduce the desired elements into the glass; thus, any of the following could be used in the batch from which the glass is prepared if added in the proper amounts to give in the final glass `the :Component:

calculated luorine .and .oxide contents specified and to give the potassium an'd tluorine in the required ratio:

lndorder to -better illustrate our invention,A the follow- .i-ngexamples `of glasses andthe preparation thereof are given. These examples, however, are givenfor the purpose of illustration onlyand should not be `interpreted as limiting the invention to the specific examples employed ,since it isfobvious that one skilled in the art, after `reading the disclosure, .could prepare many other specific :formulations differing from Ithose. set forth in the specific examples, and yet coming ywithin the spirit an-d teaching ot' our invention.

EXAMPLE l Tho-following calculated glass composition was prepared from the batch composition also set forth:

Calculated Vglass* composition Weight percent Aa 14.0 .B203 20.4 SOZ 19.9 KBO 20.7 .Fr 25.1

Batch composition Component: Weight percent Alumina hydrate, A1203.3H2O 19.0 Boric acid, H3B03 32:1 Silica, Si02 l6.0 Potassium uosilicate, K2SiF6 42.9

The materials used in making up the batch were C. P. alumina hydrate, C. P. boric acid, powdered llint and a commercial grade potassium fluosilicate (minimum'97% KgSiFS). The batch ingredientswere thoroughly mixed andplaced in an open tire-clay crucible. The open Crucible with its contents was then placed in a furnace at a temperature of between 980 and l000 C. An hour later the molten glass was ready for fritting, which was done by pouring'the molten material into cool water which was stirred during the process. The frit was then separated from the water, air-dried over-night at room temperature, and then nally driedat a temperature of to 150 C.

EXAMPLE 2 The following calculated glass composition was prepared from the batch composition given, in a manner similar to that set forth in Example 1:

Calculated glass composition' Component: Weight percent lAlO3 ,-13.9 B203 20.6 SiOZ 20.0 kKHO 20.6 F v24a as well as those com- "7 Batch composition Y Weight percent Component:

Alumina hydrate, Al,'O,.3H,O 20.0 Boric acid,H,BO3 15.2 Silica, SiO," 18.8 Potassium tluoborate, KBF4 38.8 Potassium carbonate, K,ACO3 4 7.2

The same raw materials were used as described in Example .l `with the exception ofthe potassium fluoborate which was a` commercial grade l'material` and the potassium carbonatewhichwas of C. P. grade.

i VTheglass,compositii'mof this'example.` was obtained by replacing 5% -by weight VoffA103 by Sb203. The

calculated glass composition and the batch composition from which itwas'obtained are as follows:

Calculated glass' composition` The glass was prepared in substantially the same manner as illustrated in Example l.

`\ EXAMPLE 4 This example illustrates a still further manner of vary mg the nal glass which consists in adding other ingredientstothe glass composition after it has been formed and thereafter remelting the mixture. The following calculated glass composition was obtained by adding 5 parts 'by weight of aluminum lluoride to 95 parts by weight of a glass having the calculated composition of A. The -nal glass had the calculated composition of B.

`Calculated glass composition Alumina, A1103 17. 5 16. 6 Borlc Oxide, B101.. 5.0 4. 8 Silica 27. 5 26. 1 Potassium Fluosillcate, KgSiF. 60.0 47. 5 Aluminum fluoride, AIF; 5. 0

For convenience, the second method of calculation heretofore setforth is used. This is the method in which the potassium fluosilicate is considered as KF and SiF4.

We havediscovered that the adherence of the enamels of our invention to aluminum is dependent in part on the method employed in enamelingthe aluminum. Though enamel surfaces have been obtained by dusting a dry frit on the surface tobe enameled and then tiring, we have foundl that better adheren'ceof theenamel coating tothe aluminum surface can be obtained if a slip of the frit in water is rst prepared and `this slip then applied, for

:andthereafter'allowed to cool in air.

example, by spraying,'and thereafter tired. Though vbetterladhere'nce ofthe enamel is obtained by first preparing a slip, `the resistance of the enamel coating to chemical attack thus obtained isy inferior to the resistance 'of enarnels prepared by dusting the dry frit onto the aluminum surface and. then firing; In order to obtain the particular advantages offered by`each of these procedures,1we prefer tol rst prepare an enameledsurfaee on the aluminum article by spraying or otherwise coating with aslip of the glass used, tiring, and thereafter dusting .the enameled surface with a dry powder frit of the glass EXAMPLE 5 An aluminumgpanel was irst cleaned by immersion for 'five minutes in a phosphoric acid type cleaner. Other cleaners `whiclifw'ould.satisfactorily remove organic material and dirt could be used inplace of thephophoric acid cleaner ifdesired. The cleanedpanel was rinsed with water, air dried, then dried in an oven at about 90 C.,

A slip was prepared vfrom ya frit o f the glass composition of Example 1 byplacing in a porcelain ball mill 42 parts by weight frit, l part by weight of an enameling clay, and `57 parts by weight water. The mixture was milled until less than 6% -of the solids were retained ou a 200 mesh screen. This slip was sprayed onto the cleaned panel with a conventional spray gun at a gauge pressure of about 30 pounds per square inch. Best results were obtained when thecoating had a wet weight of about 18 to 20 gms. nper' square foot which corresponds to a fired weight of about ll to 15 gms. per square foot. The slip-coated panel was air dried for a short time and thereafter fired at 530 to 550`C. for three to tive minutes. The red panel was then removed from the furnace and dustedmwith a cover-coat formed from Glass 5 of the table of glasses'heretofore given. The dusting was done through an 80 mesh screen, the'dusted coat weighing approximately l2 gms.. per .square foot. The panel was then fredagain for approximately three minutes at a temperature of 530 to 550 C. Two additional dusted cover-coats were applied in the same manner. The temperature of firing for both the slip and the dust coat are, of course, dependent uponthe fusion temperature of the glass used.

The dust coat was prepared `from glass 5 by rst preparing a frit as described in Example l and thereafter milling the frit until it screened through a mesh sieve.

Glasses of -our. present invention, though primarily suited for enameling, may have numerous other uses. F or example, we have `found that some of these glasses make excellent iillersfand bonding materials for use in abrasive wheels, are suitable as'opal glasses and form the basis for y low fusion pottery glazes, tile glazes, etc.

The glasses and frits of` our present invention `are new .products of manufacture as are also the aluminum articles whose surfaces have "been enameled through the use of frits prepared from the glasses disclosed.

Vln describing the invention, certain specic forms have been used. However, the invention may be embodied in any specific form which would be apparent to one skilled in the art without departing from the spirit and essential features of the invention. The specific examples and descriptions employed, therefore, should be considered as illustrative and not restrictive in interpreting the inven tion, and the invention should not be limited to the specific examples employed.

Having thus described our invention, we claim:

l. A glass composition consisting essentially of, on a calculated oxide basis, uorine and compatible metal oxides including K20, S102, and at least one material of the group consisting of A1203 and B203 in which the iluorine to K20 ratio is within the range of from 1.0 to 1.4, in which the calculated percent by weight of fluorine is 14% to 32% and that of X20 is 12% to 26%, and in which the percent by weight of A1203, S102 and B203 with respect to iluorine is within the limits defined by the areas labeled glass formation in the graphs shown in Figures 4a, 4b and 4c respectively of the drawings.

2. A glass composition consisting essentially of, on a calculated oxide basis, uorine and compatible metal oxides including K2O, A1203, Si02 and B202 in which the fluorine to K20 ratio is within the range of from 1.0 to 1.4, in which the calculated percent by weight of uorine is 21% to 28% and that of K20 is 17% to 23%, and in which the percent by weight of A1203, Si02 and B203 with respect to uorine is within the limits defined by the areas labeled glass formation in the graphs shown in Figures 5a, 5b and 5c respectively of the drawings.

3. A glass composition of claim 2 prepared by fusing a batch of which at least 90% consi-sts of the materials potassium uosilicate, silicon dioxide, a material of the group consisting of boric acid and boric oxide aud material of the group consisting of aluminum hydroxide and aluminum oxide, said materials being used in the calculated amounts necessary to give the percentage compositions of claim 2. l

4. The glass composition of claim 2 which was prepared by adding at least part of the calculated Si02 as Si02 in the batch igredients used in preparing the glass 10 f and in which the ratio of said added S102 to said calculated B203 is at least 1.

5. An enamel frit for enameling aluminum and aluminum alloy surfaces prepared from the glass composition of claim 2.

6. As a new article of manufacture an aluminum surface having a closely adherent enamel coating thereon comprising a glass composition as defined in claim 1.

7. A glass composition consisting essentially of, on a calculated oxide basis, 21 to 28% tluorine, 17 to 23% H20, 11 to 38% Si02, 5 to 33% A1203 and 2 to 43% B203 in which the calculated uorine and K20 are present in the relative amounts of 1.0 to 1.4 parts iiuorine per part of K2O.

References Cited in the le ofV this patent UNITED STATES PATENTS 38,286 Cobley Apr. 28, 1863 1,230,958 Warga June 26, 1917 2,165,554 Kreidl July 11, 1939 2,229,524 Rosenberg Jan. 21, 1941 2,247,196 Goodwin June 24, 1941 v 2,330,129 Lucas Sept. 21, 1943 2,475,469 Bennett July 5, 1949 2,495,837 Porter Ian. 31, 1950 FOREIGN PATENTS 138,023 Austria 1934 638,710 Germany 1936 603,623 Great Britain June 18, 1948 

7. A GLASS COMPOSITION CONSISTING ESSENTIALLY OF, ON A CALCULATED OXIDE BASIS, 21 TO 28% FLUORINE, 17 TO 23% K2O, 11 TO 38% SIO2, 5 TO 33% AL2O3 AND 2 TO 43% B2O3 IN WHICH THE CALCULATED FLUORINE AND K2O ARE PRESENT IN THE RELATIVE AMOUNTS OF 1.0 TO 1.4 PARTS FLUORINE PER PART OF K2O. 